The invention relates to an extrudable adhesive composition of ethylene vinyl acetate copolymer, modified ethylene vinyl acetate copolymer (EVA), and styrene homopolymer, useful for bonding polystyrene to gas barrier polymers.
Laminates of polystyrene and a gas barrier resin, using adhesives containing EVA modified with ethylenically unsaturated carboxylic acid or anhydride are known in the art. For example, U.S. Pat. No. 4,576,995, to Nakabayashi et al., discloses an adhesive for bonding ethylene/vinyl alcohol copolymer and polystyrene, which comprises a modified ethylene/vinyl acetate copolymer obtained by graft-copolymerizing a styrenic vinyl monomer and an alpha, beta-unsaturated carboxylic acid to an ethylene/vinyl acetate copolymer. Laminates prepared therefrom are valuable as a deep draw forming material with enhanced gas barrier properties.
Japanese application No. 53018653 (reported as Derwent Abstract No. 26079A/14) describes a low temperature heat sealing adhesive consisting of 100 parts carboxylated ethylene vinyl acetate copolymer and 3-100 parts styrene resin of molecular weight 500-1000.
Japanese application No. 54057582 (reported as Derwent Abstract No. 46260B/25) discloses a resin laminate of a polystyrene resin layer, a layer of ethylene-vinyl acetate copolymer saponification product, and a layer of a styrene/butadiene block copolymer containing 60% butadiene, ethylene vinyl acetate copolymer (6 mol % VA), and a maleic anhydride-ethylene vinyl acetate graft copolymer (3 mol % VA).
Japanese application No. 58203043 (reported as Derwent Abstract No. 84-008480/02) discloses a similar laminate, in which the adhesive layer is a blend of polystyrene, ethylene-vinyl acetate copolymer (5-50 % VA), and a polyolefin grafted with e.g. maleic anhydride.
Japanese application No. 59055743 discloses a process for production of resin laminates characterized by melt coextrusion of a styrene group resin layer, a gas barrier resin layer such as saponified ethylene-vinyl acetate copolymer, and a bonding layer of (a)ethylene- vinyl acetate copolymer graft-modified with unsaturated carboxylic acid or anhydride, and (b) ethylene-vinyl acetate copolymer which is graft-modified with e.g. styrene, or further (c) unmodified ethylene-vinyl acetate copolymer.